Diacetyl: The NCA Coffee Industry Guide

What the science says about diacetyl — and what the coffee industry needs to know.

What Is Diacetyl?

Diacetyl is a chemical compound found in many foods and beverages, including milk, cheese, yogurt, citrus juices, vinegar, whiskey, wine – and coffee.

In coffee, diacetyl is naturally produced in the roasting process. It is also found as naturally-occurring at low levels in some added flavorings.

The U.S. Food and Drug Administration (FDA) says that diacetyl is safe for consumption. Coffee drinkers are not at risk from diacetyl exposure.

However, diacetyl is starting to receive more attention with respect to its safety in e-cigs and vapes (both inhaled directly into the lungs), and also regarding workers in food and flavor manufacturing facilities (including bakeries, breweries, and coffee roasters).

Diacetyl & Worker Safety

Diacetyl, and the compound 2,3-pentanedione, are part of a family of compounds that have come under increased scrutiny resulting from potential safety concerns for workers.

Inhaling high levels of airborne diacetyl is suspected by some of being linked to the very rare, serious lung disease known as bronchiolitis obliterans (BO), which is infrequently found in the general population. This potential link first came to popular attention as so-called “popcorn lung,” after the diagnosis of workers from a butter flavoring manufacturing plant. The case subsequently resulted in new safety recommendations for exposure to diacetyl from the National Institute for Occupational Safety and Health (NIOSH).

Diacetyl and Coffee Roasting

The science behind diacetyl exposure is complex – even for the experts – and there is limited research on the topic. As a result of this complexity and limited data, there are a wide variety of recommendations regarding exposure to diacetyl.

As a result, these recommendations, known as “Occupational Exposure Limits” (OEL), have varied drastically across governmental and scientific organizations. Part of the challenge of assessing risk is that these recommendations are based on different modeling methods and types of data.

Together, the limited reported incidence of BO in the population, small pool of available research, wide range of recommended OELs, and technical complexity of the issue present a challenge to businesses that are looking to take any necessary steps to efficiently and effectively mitigate the potential risk of diacetyl exposure in their own facilities.

What the Science Says

To help NCA members better understand this issue, the National Coffee Association has been working with scientists and experts from across the industry:

NCA has commissioned a comprehensive review of the existing scientific literature regarding diacetyl and its potential linkage to disease. This review, conducted by third party expert scientists using advanced modeling techniques, showed no direct link between diacetyl exposure from coffee roasting and bronchiolitis obliterans.

The NCA requested that same scientists who conducted the literature review also review the various recommended OELs, to recommend a conservative (or erring on the side of protection) OEL for the coffee indstry.

Because diacetyl is a highly volatile substance – meaning it dissipates quickly – it is important that, when testing for its presence, a standard and proper testing protocol be followed. NCA has commissioned industrial hygienists to set forth such a testing protocol.

This NCA-commissioned literature review, OEL, and testing protocol will be made available after the literature review and OEL undergo a peer-review process for publication in a peer-reviewed scientific journal, so that this work is independently validated. Publication is expected before the end of 2018.

What the Coffee Can Industry Do

As every manufacturing and coffee roasting situation is different, the NCA cannot offer specific advice regarding any individual circumstances. However, there are general principles and resources to keep in mind.

Capturing and ventilating diacetyl is one of the most critical factors to consider in any facility. Most larger commercial roasters and equipment are “closed systems,” designed to capture and expel emissions to reduce worker exposure, while small-batch and individual roasters are more likely to be using “open” systems.

Measuring emissions and assessing ventilation should be conducted by a licensed, accredited professional. If mitigation steps are taken as a result, or if there are changes in the roasting procedure, re-inspection by such a professional may be needed.